The present invention relates to crosslinked fluorinated polymers modified with hydrogenated monomers, the processes for their preparation and the manufactured articles therefrom.
In particular the invention relates to melt-processable curable compositions, comprising thermoprocessable copolymers of ethylene (E) with tetrafluoroethylene (TFE) and/or chlorotrifluoroethylene (CTFE) modified with acrylic monomers, which subjected to thermal treatment improve their mechanical properties at high temperatures and chemical resistance, increasing their rating. Said crosslinkable compositions adhere to hydrogenated polymers.
The improvement of the mechanical properties at high temperatures is shown by the increase of the stress at break without jeopardizing the elongation at break.
The use of hydrogenated polymers in the car industry for preparing fuel hoses and fuel lines is known in the prior art. Examples of hydrogenated polymers are polyamides, polyvinylchloride (PVC), nitrile rubbers (NBR). The drawbacks of the manufactured articles obtained therefrom are the low chemical resistance and high permeability to gasolines and oils, in particular SF(copyright) oils which show high aggressivity towards the vinylidene fluoride (VDF)-based elastomers, presently used in the car industry. A high permeability to there fluids, in particular gasolines, implies a high emission of dangerous substances to the environment. The laws of most countries are more and more restrictive on these emissions due to their environmental impact. Therefore, materials having a lower permeability, improved chemical resistance and at the same time having improved mechanical properties at high temperatures, in particular stress at break, are required.
Fluorinated polymers having an improved chemical resistance to gasolines and to particularly aggressive oils used in the car industry in comparison with hydrogenated polymers, are known. Besides, said fluorinated polymers have a combination of mechanical properties which make them suitable for the above mentioned uses. The drawback of these fluorinated polymers is the high cost which limits their use.
In order to make economically possible the use of fluorinated polymers it has been suggested the use of composites of hydrogenated polymers with fluorinated polymers. However the adhesion between fluorinated polymers and hydrogenated polymers is very poor. The research is directed to find solutions such as to make possible these composites. In particular for the thermoprocessable fluorinated of ethylene (E) copolymers with tetrafluoroethylene (TFE) and/or chlorotrifluoroethylene (CTFE), for example Halar(copyright) commercialized by Ausimont USA Inc., the solutions suggested for their coupling with hydrogenated polymers, use adhesives of various types. In this case the technologies for obtaining multilaminates from the industrial point of view are more complex for the introduction of an additional adhesive layer (tie-layer technology).
The need was felt to make multi-layer manufactured articles, made of hydrogenated and fluorinated polymers having improved mechanical properties, impermeability and chemical resistance to liquid fuels without using the tie-layer technology. Among the most known applications of multi-layer manufactured articles, fuel hoses (hydrogenated rubbers/fluorinated polymers) and fuel lines (polyamides/fluorinated polymers) can be mentioned.
The Applicant has surprisingly and unexpectedly found melt-processable curable compositions comprising: thermoprocessable copolymers of ethylene (E) with tetrafluoroethylene (TFE) and/or chlorotrifluoroethylene (CTFE) modified with acrylic monomers and a cross-linking agent, which subjected to thermal treatment are capable to crosslink, improving their mechanical and chemical resistance properties, showing adhesive properties with hydrogenated polymers.
An object of the present invention are therefore melt-processable thermally crosslinkable compositions comprising:
I) thermoprocessable copolymers of ethylene (E) with tetrafluoroethylene (TFE) and/or chlorotrifluoroethylene (CTFE) modified with acrylic monomers of formula:
CH2xe2x95x90CHxe2x80x94COxe2x80x94Oxe2x80x94R2xe2x80x83xe2x80x83(a)
R2 is an hydrogenated radical from 1 to 20 carbon atoms, C1-C20, alklyl, linear and/or branched radical, or cycloalkyl, or R2 is H. The radical R2 can optionally contain: heteroatoms preferably Cl, O, N; one or more functional groups preferably selected from OH, COOH, epoxide, ester and ether; and double bonds; the above n is an integer in the range 0-10.
II) one or more cross-linking agents.
The thermoprocessable copolymers of the present invention composition comprise from 10 to 70%, preferably from 35 to 55%, by moles of ethylene, from 30 to 90%, preferably from 45 to 65%, by moles of a fluorinated monomer selected from tetrafluoroethylene, chlorotrifluoroethylene, or mixtures thereof, from 0.1 to 30%, preferably from 1 to 15% by moles of the comonomer (a).
As component I), thermoprocessable copolymers wherein the fluorinated monomer is chlorotrifluoroethylene are preferred. n-Butylacrylate (n-BuA) is the preferred acrylic monomer.
The cross-linking agents can be active by radical way, such as for example The cross-linking agents can be active by radical way, such as for example traallylisocyanurate (TAIC), triallylcyanurate (TAC), diallylisophthalate (U.S. Pat. No. 4,039,631), diallylterephthalate (U.S. Pat. No. 4,039,631,), esters of phenylindan dicarboxylic acids (U.S. Pat. No. 3,763,222), triallyl esters of aryl polycarboxylic acids (U.S. Pat. No. 3,840,619), bis-olephins such as for example 1,6 divinylperfluorohexane (see U.S. Pat. No. 5,612,419) and others (see U.S. Pat. No. 4,121,001); or active by ionic way such as for example hexamethylendiaminecarbamate (DIAK 1), N,Nxe2x80x2-dicinnamylidene-1,6-hexanediamine (DIAK 3), maleimide derivatives such as for example m-phenylenebismaleimide, C4-C20 aliphatic diamines, polyhydroxyl aromatic compounds for example bisphenols A, AF and S. As crosslinking agents active by radical way triallylisocyanurate is preferred. As crosslinking agents active by ionic route aliphatic and aromatic diamines are preferred.
The cross-linking agent amounts ranges from 0.1 to 20.0% by weight, preferably from 0.5 to 10.0%, more preferably from 1.0 to 5.0%.
The crosslinkable melt-processable compositions can furthermore contain one or more optional ingredients such as fillers (for example polytetrafluoroethylene (PTFE), silicates), smoke retarders, lubricants, pigments, fire retardants, intumescent agents, plasticizers (for example MORFLEX(copyright) 560), metal oxides (ZnO, MgO), inorganic bases (Ca(OH)2), tetraalkyl ammonium or phosphonium salts, thermal stabilizers such as for example Irganox(copyright) 1010 and peroxides used in crosslinking processes known in the prior art, for example Luperco(copyright) 101 XL (2,5-dimethyl-2,5-di(terbutylperoxy)hexane 45% by weight on inert support), dicumylperoxide.
The maximum total amount of the optional components is 30.0% by weight.
The composition of the present invention is obtainable by closely mixing the ethylene thermoprocessable copolymers with tetrafluoroethylene (TFE) and/or chlorotrifluoroethylene (CTFE) modified with acrylic monomers, with one or more crosslinking agents. Alternatively, the composition of the present invention can be obtained by homogeneously distributing one or more crosslinking agents on a manufactured article of thermoprocessable copolymers of ethylene with tetrafluoroethylene (TFE) and/or chlorotrifluoroethylene (CTFE) modified with acrylic monomers, or by contacting the surfaces of said manufactured article with a hydrogenated polymer containing one or more crosslinking agents.
A further object of the present invention is a crosslinking process consisting of subjecting the melt-processable crosslinkable compositions of the present invention, to a thermal treatment.
Such a process is carried out at a temperature generally higher than 15 xc2x0C. When the crosslinking agents are activated by ionic way, the process is carried out at temperature preferably lower than 200xc2x0 C. When the crosslinking agents are activated by radical way, the process is carried out at a temperature preferably higher than 250xc2x0 C.
For a given composition of the invention, the time of the thermal treatment decreases as the chosen temperature for the crosslinking increases.
A further object of the present invention are the manufactured articles obtained by crosslinking the melt-processable compositions of the present invention.
A further object of the invention are multi-layer manufactured articles of hydrogenated polymers and melt-processable crosslinkable compositions of the invention, thermally treated and untreated. The preferred manufactured articles are: fuel lines, obtainable for example by coextrusion of polyamide and the compositions of the invention; fuel hoses, obtainable for example by extrusion of hydrogenated rubber on a tube made of the compositions of the invention.
As hydrogenated polymers we can mention thermoplastics and elastomers. As thermoplastic polymers: for example cellulose polymers, polyamides such as NYLON 6, NYLON 66, NYLON 11, NYLON 12, polyamide copolymers, polycarbonates, polyesters, such as polyethylenterephthalate, polyester copolymers, polyolefins such as high and low density polyethylene, olefine copolymers, polyimides, polystyrene, polyurethanes, polyvinylchloride (PVC), polysulphones, ethylene/vinylacetate copolymers, polyacrylbutadienestyrene (ABS). The preferred thermoplastic hydrogenated polymers are polyesters, polyolefins, polyamides.
As hydrogenated elastomers we can mention acrylic rubbers, nitrile rubbers (NBR), ethylene-propylene rubbers (EPM), ethylene-propylene-diene rubbers (EPDM), NVC rubbers (nitrile NBR rubbers mixed with PVC), epichlorohydrin rubbers (CO and ECO).
As hydrogenated elastomers, epichlorohydrin and nitrile rubbers (NBR) are preferred.